1. Field of the Invention
The present invention relates to a monolithic piezoelectric body and a piezoelectric actuator, and more particularly, to a monolithic piezoelectric body and a piezoelectric actuator which may be used in a printing head of an ink jet printer.
2. Description of Related Art
Conventionally, a piezoelectric actuator has been used to drive a printing head of an ink jet printer. First, an example of a conventional piezoelectric actuator will be described with reference to FIGS. 6 through 8.
FIG. 6 is a perspective view of a conventional monolithic piezoelectric body used for producing a piezoelectric actuator. In FIG. 6, a monolithic piezoelectric actuator 51 having a rectangular parallelepiped shape is made of a sintered ceramic body 56 which is produced by firing a monolithic body including piezoelectric ceramic sheets and internal electrodes.
In order to produce the sintered ceramic body 56, as shown in FIGS. 7A and 7B, a ceramic green sheet 52 has an internal electrode 53 printed thereon, and a ceramic green sheet 54 has an internal electrode 55 printed thereon. Subsequently, a plurality of ceramic green sheets 52 and a plurality of ceramic green sheets 54 are alternately laminated to form a laminate body. The layers and components of the laminate body are pressed in the thickness direction thereof and fired, to thereby obtain the monolithic sintered ceramic body 56.
The internal electrodes 53 are exposed at a portion of a side surface 56a of the sintered ceramic body 56 as well as at side surfaces 56b and 56c of the sintered ceramic body 56. The internal electrodes 55 are exposed at a region isolated from the internal electrodes 53 on a side surface 56a of the sintered ceramic body 56, as well as, at side surfaces 56c and 56d of the sintered ceramic body 56.
External electrodes 57 and 58 are disposed on the side surface 56a of the sintered ceramic body 56. The external electrode 57 is isolated from the external electrode 58. The external electrode 57 is electrically connected to the internal electrodes 55, while the external electrode 58 is electrically connected to the internal electrodes 53.
During use, the monolithic piezoelectric body 51 is driven via application of AC voltage between the external electrodes 57 and 58.
In order to drive a printing head of an ink-jet printer, a plurality of actuator units must be formed from the above-described monolithic piezoelectric body 51.
A plurality of slits A are formed in an upper surface 56e of the monolithic piezoelectric body 51 such that the slits A extend from the side surface 56a to the side surface 56c, to thereby form a plurality of actuator units 60-63. The thus-formed conventional piezoelectric actuator 59 is illustrated in FIG. 8.
The slits A divide the external electrode 58 into a plurality of external electrodes 60a-63a, which are electrically connected to first internal electrodes of the piezoelectric actuator units 60-63, respectively.
However, second internal electrodes of the piezoelectric actuator units 60-63 are not electrically connected to the external electrode 57. That is, the internal electrodes 55 formed in the monolithic piezoelectric body 51 are divided by the slits A, so that electric connection between the second internal electrodes and the external electrode 57 is broken.
Therefore, the second internal electrodes formed by division of the internal electrode 55 shown in FIG. 7B must be connected to an electric power source on the side surfaces of the piezoelectric actuators 60-63 disposed opposite to the side surface 56a; i.e., the side surface 56c of the sintered ceramic 56. More specifically, external electrodes are disposed on the side surface 56c, and the external electrodes are connected to the power source. Thus, in the actuator 59, electric connection to an electric power source and other elements via conductors such as lead wires must be established on two side surfaces 56a and 56c.
Therefore, the conventional monolithic piezoelectric body and the piezoelectric actuator have several disadvantages including high production cost and insufficient reliability.